We evaluated Microsoft Teams and in fact ran our first webinar using Teams two weeks ago. In comparison, I don't feel that GotoWebinar has the range of customization and it feels quite antiquated in comparison to Teams. We also tried WebEx and we were able to make it work but it wasn't great for webinars and felt more antiquated than GoToWebinar and was lacking sufficient functionality. It was a legacy product that we had from our global headquarters, and may have evolved since I used it. We're migrating toward Teams now. 

We would try other solutions out for a few weeks, then we would have problems. So after trying out so many other ones, we just finally found GoToWebinar, and it was the best for the time.

I am currently evaluating several web conferencing solutions including Adobe Connect Learning, WebinarJam, Livestorm, and Blackboard.